Process and apparatus for photolytic degradation of explosives

ABSTRACT

A process for photolytic degradation of the organic and nitrogenous components of high explosives in organic solvent is described. The process can be applied with a module photolytic apparatus so that munitions can be destroyed without endangering the environment or toxifying large quantities of water. An apparatus is also disclosed.

BACKGROUND OF THE INVENTION

The explosive power of so-called secondary explosives and certaininitiating explosives used in most modern munitions has been developedto a remarkable degree of destructiveness. This is due in part to theuse of several components in the explosive. Consequently, not only arethe primary detonation products factors generating the destructive forcebut also the secondary combustible gases and heat of reaction. Theformer are produced by the metastable nitrogenous and organic compoundspresent. The latter are produced by metal powders and oxidizersincorporated into the explosive.

Processes for disposing of such secondary explosives in munitions havetypically involved non-confined detonation, incineration, or openburning. To obtain the explosive from the munitions, the munitions areoften opened by sawing or mechanical cleaving. This process enablesreclamation of the metal munition housings or shell. However, aside frombeing very dangerous, these techniques result in release of largequantities of toxic and/or otherwise undesirable compounds into the air,ground and ground water.

Disposal efforts have also included slicing the munitions open andwashing out the explosive with water. This process results incontamination of large quantities of water with the recovered explosiveand explosive byproducts. This water is toxic to aquatic life and cannotbe returned to the environment without removal of the explosives. Someeffort has been devoted to development of methods to remove theseexplosives from water. In particular, activated carbon such as carbonblack or charcoal will absorb much of the explosive and has been used totreat the water solutions formed by washing the explosive from theopened munitions. Not all of the explosive is removed from the water,however. Moreover, the carbon treatment results in additional processingof the carbon which can retain as much as 0.5 grams of explosive perkilogram of carbon.

Several other processing methods have been proposed for treatment of theexplosive waste water. Photolysis by ultraviolet irradiation of theexplosive-laden water will cause degradation of the explosive compoundsto neutral and stable compounds such as ammonia and carbon dioxide.Typically, the ultraviolet photolysis can be catalyzed with free radicalsources such as ozone or hydrogen peroxide to facilely produce unstableintermediates from the explosives.

This development of degradative processes for explosives is exemplifiedby Andrews et al, U.S. Pat. No. 4,038,116, which discloses a method fordegrading aromatic explosive solutions such as nitrotoluenes,nitramines, anti other explosives through the application of ultravioletenergy. Andrews notes that the degrading reaction may be catalyzed bythe induction of reactive intermediates through the use of free radicalinitiators such as acetone or hydrogen peroxide. The Andrews processultimately produces such byproducts as carbon dioxide and ammonia.However, Andrews initiates his process by "solubilizing" the explosivesinto a water solution and mixing it with the reactive intermediate.

Problems of the Andrews process include the low, almost null solubility,of organic explosives in aqueous solvent (in the magnitude of 10 ppm).Furthermore, the batch mode processing of Andrews means that a portionof the aqueous explosive solution is processed by recirculation untilall measurable amounts of the explosive are removed. This is a timeconsuming and labor intensive exercise. Wholly apart from the technicalproblems, the negligible solubility of explosive in water breedssignificant impractibilities because vast quantities of water would berequired for processing. Therefore, any sort of modular water reactorsystem for on-site treatment of weapons caches could not be developed.Moreover, the rate of destruction of the explosives is limited due tothe very small concentrations of the explosive in the aqueous system. Asa result, the method of Andrews et al as well as other aqueous basedprocesses for degradation of explosives fail to provide continuousprocessing of the explosives.

Such aqueous treatment systems for disposal of munitions are dangerousas well. The addition of water to explosives in the context of a systemhaving the potential for oxidation and generation of heat often providesjust that element needed to cause spontaneous combustion or explosion ofthe munition. This element is especially prevalent when metal powder ispresent as it is in most modern explosives. The metal powder is oftenencapsulated by a coating agent such as a fatty acid salt. Theencapsulation prevents spurious contact of water and the metal powderbut also prevents appropriate aqueous treatment and separation.Moreover, when an aqueous disposal system does penetrate to the surfaceof the metal powder, the result is often a conflagration. The metalpowder is highly reactive with the water. In other respects, however, anaqueous system would seem to be the safest. Its non-combustibility inthe presence of flame, heat and sparks would minimize the accidentalincineration of the explosive.

Therefore, it is an object of the invention to provide a process fordegradation of explosive organic compounds or munitions that enables theuse of continuous processing of more concentrated forms of explosive. Afurther object is the development of a safe process that avoids theexplosive potential of aqueous systems. Yet another object is thedevelopment of an integrated process for removing the explosive from themunition and converting it to non-explosive chemicals.

SUMMARY OF THE INVENTION

These and other objects are achieved by the present invention which isdirected to a process and apparatus for safe conversion of highexplosives into non-explosive byproducts. The process is based upon theuse of organic solvent to dissolve or disperse the organic components ofthe explosive, prevent reaction of the powdered metal components withwater and enable the photolysis of the nitrogenous and organic explosivecomponents. The apparatus includes components for removing theexplosive, for dissolving or slurrying it and for irradiating thesolution or slurry.

In a first aspect of the process, a pressurized jet or stream of organicsolvent opens the munition to expose the explosive, removes theexplosive from the munition and forms a mixture with the explosive.Preferably, the jet of organic solvent is continuous and/or carries aparticulate abrasive.

In a second aspect of the process, the mixture (solution or slurry) oforganic solvent and nitrogenous and organic components of the explosiveis photolyzed under ultraviolet conditions within a region of the UVspectrum where the explosive absorbs energy. The photolysis degrades theexplosive to non-explosive byproducts such as carbon dioxide, water andnitrogen. The byproducts may be readily removed from the organic solventowing to their differing phase or low solubility in the solvent.

Several versions of the process are available including an integratedtwo stage version and a single stage version. In the integrated versionof the process, the mixture produced by the solvent jet is directlytransported to the photolysis stage preferably through a solvent recycleloop. In a single stage, the explosive is typically in bulk rather thanpacked in a munition. The explosive is dissolved or dispersed in organicsolvent and the resulting mixture is photolyzed.

Mixtures of solvent can be employed at the various stages of theprocesses so that a solvent appropriate for jetting and cutting isthereafter combined with a solvent which will dissolve or dispersesignificant amounts of the organic components. With all versions, thesolvent(s) can be recycled and can be applied or used under variousconditions of temperature and pressure. These options provide for hightemperature, high pressure operations that will favor increasedsolubility of the explosive in the solvent.

The apparatus generally includes components in fluid connection foraccomplishing the processing steps. In particular, the apparatus is thecombination of a variable high pressure cutting and excavating jetcomponent, a collection vessel for the excavated explosive and solvent,a pumping means for transporting the solution or slurry among thecomponents and a UV reactor for irradiation of the solution or slurry.

Accordingly, the invention provides a continuous system process andapparatus for converting highly concentrated solutions of explosives tonon-explosive byproducts. The process and apparatus enable a modularprocessing station for the degradative conversion of explosive compoundsand compositions. By using a closed system, the required solvent isminimized and the potential for environmental contamination issubstantially eliminated. Furthermore, the use of organic solventeliminates the hazard of explosion attendant with the use of aqueoussystems for degradation of explosives.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic representation of the cutting and photolyticprocess.

FIG. 2 is a cutaway plan view of the reactor module in accordance withone embodiment of the invention.

FIG. 3 is a cutaway perspective view of one embodiment of theultraviolet lighting configuration in accordance with the invention.

FIG. 4 is a drawing of a cascade irradiation device using an opticalfiber network or UV lights.

FIG. 5 is the schematic representation of a photolytic process withfiber optics in accordance with one aspect of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention for disposal of modern explosive mixturesvirtually eliminates accidental conflagration which can be caused byreaction of water and the metal powder component of the explosive. Theorganic solvent used to dissolve the nitrogenous and organic componentsof the explosive acts as a liquid barrier to prevent contact of themetal powder with water either in the air, from degradation of thenitrogenous organic components of the explosive, or as a minoringredient of the solvent itself. At the dissolution step, the metalpowder is separated from the organic components of the explosive, suchas by agglomerating on the bottom of the separatory vessel, and can betransported to another vessel for safe disposal.

Explosive, in the context of the invention, means any secondary chemicalexplosive or other chemical compound or composition found in munitionswhich is capable of deflagration by shock from a primary explosive sothat rapid production of large quantities of hot gas results or selectedprimary explosives that have functions other than exclusively asdetonators. These explosives exhibit absorption in the ultravioletspectral band. Examples of such chemicals include ammonium nitrate (AN),ammonium perchlorate (AP), benzotris[1,2,5]-xadiazole,1,4,7-trioxide(BTF), 2,4,6-trinitro-1,3-benzenediamine (DATB), 2,2'-oxybisathanol,dinitrate (DEGN), 2,2',4,4',6,6'-hexanitro-[1,1-biphenyl]-3,3'-diamine(DIPAM), 2,2-dinitropropyl acrylate (DNPA), ethyl 4,4-dinitropentanoate(EDNP), ethylene glycol dinitrate (EGDN), ammonium picrate (ExplosiveD), 1,1'-[methylenebis(oxy)]bis-[2-fluoro-2,2-dinitroethane] (FEFO),octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX),bis(2,4,6-trinitrophenyl)-diazene (HNAB),1,1'-(1,2-ethenediyl)bis-[2,4,6-trinitrobenzene] (HNS), nitroguanidine(NQ), nitroglycerine (NG), 2,4,6-trinitrophenol (picric acid),hexahydro-1,3,5-trinitro-1,3,5-trazine (RDX),2,4,8,10-tetranitro-5H-benzotriazolo-[2,1-a]-benzotriazol-6-ium,hydroxide,inner salt (TACOT), 2,4,6-trinitro-1,3,5-benzenetriamine (TATB),N-methyl-n,2,4,6-tetranitrobenzenamine(tetryl), tetranitromethane (TNM),2-methyl-1,3,5-trinitrobenzene (TNT), and others including castexplosives, plastic bonded explosives and other miscellaneous explosiveswhich may be the product of one or more of the previously mentionedcompounds or other derivatives in the form of a single compound, amixture of these compounds, or the reaction product of these compounds.

Other compounds which may also be processed in accordance with theinvention disclosed herein include propellants which tend to be mixturesof such compounds as sulfur, carbon and potassium nitrate (blackpowder), dinitrotoluene, propylene glycol dinitrate, otto fuel,trinitrotoluene, nitroglycerine, nitroguanidine, dibutylpththalate,triacetone, among other constituents. Also included are certain primaryexplosives such as NG, DEGDN and EGDN.

The explosive also may contain finely divided metal and/or combustibleinorganic powder usually encapsulated in a fatty acid salt or otherbarrier coating. The metals and inorganics include any that will rapidlyor even spontaneously combust in air or water. Included are zinc,magnesium, aluminum, zirconium, iron, antimony, boron, as well as othercombustible metals. The metal powders are treated to remove oxidecoatings that prevent decomposition and coated in an inert atmosphere toavoid reintroduction of the oxide coat. Because of their high surfacearea and non-oxidized surfaces, the metal and inorganic powders arehighly reactive. Their reaction especially with water generates hydrogenwhich acts as an incendiary element in the munition.

The organic solvent for the process produces mixtures (solutions orslurries) of the nitrogenous and organic components of the explosive.The solvent is chosen so that the nitrogenous and organic components areat least significantly soluble and/or dispersable in the solvent. Theorganic solvent is preferably a polar, non-hydroxylic organic compoundthat is transparent to visible and ultraviolet light although it mayexhibit some absorption within some but not all regions of the selectedultraviolet region. Generally, the organic solvent may be chosen fromalkyl alcohols, alkyl ketones, alkyl nitriles, nitro alkanes andhalo-alkanes provided that the solvent does not substantially polymerizeunder ultraviolet irradiation conditions or act as a black solvent, i.e.absorb strongly within the ultraviolet region of the photolysis. Organicsolids that will liquify at temperatures slightly above ambient areincluded as organic solvents as well as organic liquids and gases thatcan be maintained as liquids under moderate or high pressure andmoderate or high temperature conditions. More particularly, the alkylgroup of the organic solvent may be a branched, cyclic or straight chainof from three to about twenty carbons. Examples of such alkyl groupsinclude octyl, dodecyl, propyl, pentyl, hexyl, cyclohexyl and the like.The alcohols may be composed of such alkyl groups as long as they meetthe liquid definition mentioned above. The ketones include such solventsas acetone, cyclohexanone, propanone and the like as long as they meetthe liquid definition mentioned above. The nitrile compounds includesuch solvents as acetonitrile, propyl nitrile, octyl nitrile and thelike. Examples of halogenated alkanes include methylene chloride,chloroform, tetrahaloethylene or perhaloethane and the like. Mixtures ofthe foregoing individual organic compounds can also function as theorganic solvent. Since some solvents function better as cutting agentswhile others function better as dissolving agents, a preferred techniqueis the use of one or a mixture of particular organic compounds as thecutting and removal solvent and another compound or mixture as thephotolysis solvent. Although the cutting and removal solvent can beevaporated and replaced by the photolysis solvent, it is preferred toadd the photolysis solvent to the cutting and removal solvent before theremoved organic explosive components are photolyzed. Mixtures areespecially preferred when the photolysis solvent exhibits someultraviolet absorption such as often occurs with the ketone solvents.Especially preferred mixtures include gasoline or diesel fuel or longchain hydrocarbons as the cutting and removal solvent and short chainsaturated alcohols, nitriles, halogenated alkanes and ketones such asacetone, acetonitrile, propanone, ethanol and propanol as the photolysissolvents. Organic compounds that act as photolysis inducers may also beincorporated in mixture with the organic solvent. Such compounds includeolefins and aromatic olefins such as cyclohexene, octene, stilbene andthe like.

The photolytic stage of the present invention functions to convert thenitrogenous and organic explosive components to non-explosive compoundswithout the use of further photolytic inducing agents such as freeradical initiators, photolytic inducers and the like. Preferably,however, the photolysis is conducted in the presence of a free radicalinitiator. It has been found that the rate of reaction as well as thequantum yield are increased under the influence of a free radicalinitiator. Such initiators function as a ready source of free radicalsand do not require significant input of energy for this generation. Thefree radicals produced include hydrogen, hydroxyl, oxygen and sulfurcontaining radicals. Sources include inorganic and organic peroxides,organic compounds which form stable radicals and have labile hydrogenssuch as allyl alcohol, benzophenone, unsaturated ketones and the like,and persulfites as well as persulfates. Other free radical initiatorswhich may be used in this invention include chlorinated trisodiumphosphate, potassium peroxy diphosphate, sodium peroxytoluenesulfonchloramine, potassium peroxy monosulfonate, peracetic acid, ozoneand hydrogen peroxide.

Photolytic inducers can also be included in the photolysis mixture. Suchinducers efficiently absorb ultraviolet light and transfer it to theexplosive organic components in the form of triplet energy. Suchinducers include ozone, hydrogen peroxide, benzophenone, stilbene,naphthalene, acetophenone and other highly conjugated organic compounds.

Munition Evacuation

According to the process of the invention, the removal stage generallyencompasses eroding, excavating or evacuating the explosive from themunition. After separating the munition from the propellent casing, ifnecessary, the munition housing (hereinafter casing) is opened to exposethe explosive as well as to dissolve or slurry the nitrogenous andorganic components of the explosive in a liquid organic medium.

Generally, any number of techniques may be used to open the casing suchas milling, sawing, abrasive cutting, crushing or shearing. Some areclearly more dangerous than others considering that high explosives areinvolved. A preferred technique has been developed according to theinvention. This technique is relatively safe because it does not dependupon heat, compressive pressure or a technique that could produce aspark. According to the invention, the technique calls for applicationof a steady high pressure jet or stream of the organic solvent to thecasing. The jet or stream cuts through the casing with minimumgeneration of heat, compressive pressure or sparks.

Optionally, an abrasive may be entrained in the organic solvent. Forexample a particulate abrasive may be aspirated into the jet of solventthrough an aspirating inlet at the pressure head. Abrasives which areuseful in accordance with the invention include carborundum, silica.alumina, ceramic dust, beryllia powder as well as any hard sharp-edgedparticulate matter.

Generally, solvent pressures ranging from about 1,000 psi to about500,000 psi, preferably from about 20,000 psi to 60,000 psi, and mostpreferably from about 35,000 psi to 50,000 psi will cut through thecasings to expose the explosives. In the process of opening the casing,the jet is directed to cut a line almost completely through the casingsuch that the line divides the casing in two parts. Preferably, thepressure of the jet is decreased when the jet has penetrated the casingthickness to an appropriate limit of safety. Although the jet techniqueis safer than other techniques, this safety range will prevent thekinetic energy created by the jet from detonating the explosive. Apreferred safety factor is penetration through about 95% of the casingthickness. The jet pressure for cutting the remaining thickness can besignificantly decreased so that accidental kinetic detonation isavoided.

Any of the organic solvents described above that are or will be liquidat sub-zero to high temperature will function as the cutting andremoving solvent. Aliphatic liquids and gases such as gasoline, naphtha,kerosene, and propane under pressure are also useful as such cutting andremoving solvents. Preferred organic solvents are those which have a lowenough viscosity and a high enough boiling temperature at the in-linepressures provided above to continue to move through the fluid deliverysystem and jets without clogging and without vaporizing once the jetexits the output nozzle. Organic solvents which have been found toprovide preferred viscosities include diesel fuel, kerosene andgasoline, a mixture or C6 to C10 alkanes, naphtha fuel, C3 to C7 ketonesand other long chain hydrocarbons.

Once the casing has been opened, the explosive may be removed. Inaccordance with this step of the process, the explosive may be removedfrom the casing by any number of means such as drilling, cutting,excavating, melting, slicing and the like with mechanical or heatproducing equipment. Preferably, according to the invention, theexplosive is removed (eroded, excavated or evacuated) by the jet oforganic solvent without abrasive that opened the casing. The pressure ofthe jet is reduced to a level that will enable safe removal relative tothe detonation energy level required by the explosive. In conducting theremoval, the jet dissolves or disperses portions of the explosive,erodes further portions and slices portions to produce loose solidagglomerates of explosive that are excavated from the casing by thepressure of the jet. The jet of solvent may be moved around the munitioncasing by sweeping the flow of solvent around the casing periphery tobreak free the munition. Alternatively, the solvent may be applied athigh pressure directly into the explosive held within the munitionscasing to provide a more fine crystalline particle which tends to bemore readily soluble or dispersable in the organic solvent.

The jet pressure for removing the explosive ranges from about 50 psi to200,000 psi, preferably from about 1,000 to 60,000 psi, and mostpreferably from about 1,200 to 40,000 psi. The temperature for removingthe explosive ranges from about -40° C. to 130° C., preferably fromabout 0° C. to 35° C., and most preferably from about 15° C. to 25° C.,where higher temperatures contribute to higher solubility of theexplosive in the solvent. A higher temperature may also add to theamount of kinetic energy present in the system and thus require a lowerjet pressure for the explosive removal from the casing. Lowertemperatures are preferred for desensitizing explosives during removal.

Separation of Reactive Metal

After the explosive has been removed from the casing, the reactive metalor inorganic is separated from the solvent stream before conducting thephotolysis reaction.

The explosive removal of the invention may also remove the wax or othercoating from the metal or inorganic powder. The metal or inorganicpowder does not combust or cause incineration because contact with waterand oxygen is prevented by the solvent barrier. The metal or inorganicpowder cannot be carried into the photolytic reaction, however. One ofthe byproducts of the photolysis of the organic explosive is water whichwould cause an incendiary reaction with the powder. Also, the metalpowder will reflect or block the UV light. Once the explosive isdissolved or slurried by mixing with organic solvent or through the jetremoval process, any metals present in the explosive settle, precipitateor otherwise fall to the bottom of the vessel for collection of erodedexplosive. These metals may then be left at the bottom of the vessel asan insoluble sludge while photolytic processing continues. Any suspendedmetal or inorganic powder may be removed by filtering or centrifugingand the like.

Waxes often present in explosive compositions may be separated by phaseseparation or system shocking through the addition of various solvents,temperature changes or through processing mechanisms known to those ofskill in the art.

The wax and coating components present in the explosive may be dissolvedby the organic solvent and carried through the photolytic stepsubstantially unchanged since they are essentially hydrocarbons. Theirdisposal with the organic solvent such as by combustion can be easilyobtained. If the organic solvent is recycled, the wax and coatingcomponents may interfere with the viscosity, boiling temperature andsolubilizing parameters of the organic solvent. Consequently, the waxand coating components can be removed before or after, preferably afterphotolysis by such techniques as vacuum distillation of the organicsolvent, cold phase separation by precipitation of the wax and coatingcomponents or chromatography on supports such as silica gel and the liketo allow recycling of the solvent.

The Photolysis of the Explosive

According to the invention, the photolysis of the nitrogenous andorganic components of the explosive converts them to harmless byproductssuch as carbon dioxide, water and nitrogen. In this stage of theprocess, the nitrogenous and organic components are dissolved at as higha concentration as possible in the organic solvent or are dissolved anddispersed in even higher amounts as a finely divided slurry in thesaturated solvent. Dispersing the components under the jet of organicsolvent will avoid explosions otherwise resulting from the sensitivityof finely divided dry explosive. The solvent or solvent mixture isselected to insure solubilization and/or slurrying of the nitrogenousand organic components. The organic solvents for this purpose arecharacterized in the foregoing discussion. Preferred organic solventsinclude acetonitrile, methylene chloride, acetone, nitroethane as wellas mixtures of any of these solvents or combinations.

The ratio of solvent to explosive depends upon the conversely relatedparameters of degradative efficiency and economies of concentrationespecially when processing large quantities of munitions explosives. Theconcentration of the nitrogenous and organic components within theorganic solvent may generally be about the saturation concentration inthe solvent as long as the overall system safety is not compromised orthe degradative efficiency of the system is not restricted by theability of ultraviolet light generating device to produce the neededintensity or the absorption efficiency of the solution being photolyzed.For typical photolytic conversions, the dissolved concentrations of thenitrogenous and organic components of explosives within the organicsolvent at ambient conditions may range from about 0.5 wt-% to the lowerof the solubility or propagation limit (the propagation limit being theconcentration of explosive that will continue a detonation), preferablyfrom about 1 wt-% to 10 wt-% especially up to 5 wt-%. In acetonitrile,for example, TNT has a saturation solubility of about 7 wt-%, RDXsaturates at about 4 wt-% and HMX saturates at about 1.6 wt-%.Concentrations of dissolved explosive in organic solvent may be as highas 30 wt-% or the propagation concentration limit under temperature andpressures higher than ambient. Alternatively, slurries carrying higherthan the saturation amount of explosive components (e.g., up to 30 wt-%)may be employed as long as the particulate size is small enough toassure photolytic degradation. Particles in the order of 5 to 500microns are useful in this regard.

Once prepared, the mixture is generally metered into a UV transparenttube for exposure to an ultraviolet energy source. The transparent tubeused to process the solvent/explosive composition may comprise anynumber of UV transparent glasses such as quartz glass, VYCOR™ (CorningGlass, Ithaca, N.Y.), fused silica, and the like.

Additionally, this transparent tube may take any variety of patternsincluding patterns which promote the thin film application ofultraviolet energy, a cascading pattern which allows the photolysissolution to flow over stepped flow barriers, and those systems which usereflectors to focus, concentrate, and recycle ultraviolet radiationthroughout the system. Preferred glass configurations include quartz.Preferred patterns of the transparent feed path include helix or sheets.

In processing the solvent/explosive composition, any number of sourcesfor ultraviolet light may be used. One source found preferable for itseconomy and ready availability is a cold cathode gas lamp such asmercury gas lamp. Also useful are mercury arc lamps, lasers or any otherlight source that generates spectral emission in the desired frequencyrange.

Generally, the ultraviolet wavelength range may be that absorbed by thenitrogenous and organic components of the explosive. Typically,ultraviolet light ranging in wavelength from about 200 to 400 nm,preferably from about 200 nm to 300 nm, and most preferably from about240 nm to 280 nm is appropriate according to the invention. Anynitrogenous or organic component that exhibits spectral absorption inthis range is susceptible to the process of the invention. However, theuse of ultraviolet light of a wavelength longer than 400 nm often doesnot provide adequate flux and wattage for efficient degradation. The useof ultraviolet energy below 200 nm may cause the production of radicaloxygen within the system and for that reason is disfavored.

The preferred source for production of ultraviolet energy in accordancewith the invention is a mercury vapor lamp having approximately 7 torrpartial pressure of argon and providing an ultraviolet light wavelengthof 254 nanometers. This UV source has been found to be most economical,available and adaptable to the process of the invention.

Generally, the irradiation period for the solution will depend upon theexplosive to be processed and its concentration. The higher theconcentration, the longer will be the irradiation period for a givenportion of mixture in order to achieve essentially complete conversion.Typically for tube helix configurations, irradiation periods forconcentrations of 1 to 7 wt percent explosive relative to the totalweight of mixture range from 5 to 30 minutes preferably from about 10 to20 minutes and most preferably from about 12 to 17 minutes. One aspectof the invention is its continuous solvent recycling so that smallerthan otherwise expected portions of solvent can be used to process largebatches of explosive.

The rate of the photolytic degradation may be increased by addition offree radical initiators and photolytic inducers as discussed above. Thefree radical initiators and photolytic inducers may be added to thephotolytic mixture when it is mixed following the removal stage orduring the photolysis. The initiators readily generate free radicalswhich extract radicals from the explosive components thereby causingtheir destabilization. The inducers facilely transfer photolytic energyto the explosive components also causing their destabilization.Oxidizers can also be added. These will cause cleavage of carbon bondsso that radical destabilization and byproduct generation rapidly result.Such oxidizing compounds include those using halogens such as ozone,hydrogen peroxide, sodium hypochloride, lithium hypochloride or calciumhypochloride; isocyanurate complexes such as sodiumdichloro-s-triazinetrione dihydrate, potassiumdichloro-s-triazinetrione, sodium dichloro-s-triazinetrione,trichloro-s-triazinetrione; halogen hydantoin complexes such aschlorohydantoin, bromochlorohydantoin and complexes thereof.

The free radical initiators and photolytic inducers can be added at arate ranging from about 0 to 20 wt-%, preferably from about 0.05 to 10wt-%, and most preferably from about 0.05 to about 1 wt-%. The amount ofoxidizers added to the system at any one time will vary depending uponthe concentration of organic or nitrogenous component within the solventand the desired rate of degradative photolysis.

Application of the Photolytic Process

As depicted schematically in FIG. 1, the cutting and photolytic processis accomplished by removing the explosive with a solvent jet andconducting the mixture of organic solvent and organic and/or nitrogenouscomponent through a closed photolytic system. Temperature control of theexplosive-solvent mixture is a feature of this process such that abovethe line A of FIG. 1, increased solvent temperature will enhanceexplosive solubility and below the line A of FIG. 1, reduced temperaturerelative to ambiant will desensitize explosive reactivity. An explosivecomponent storage tank and a reserve solvent tank feed the mixingchamber the desired ratio of further solvent and explosive component.The explosive component storage tank also functions as the metal andinorganic powder sludge holding tank. The sludge can be removed throughan outlet valve at the bottom of the tank. The mixture and anyinitiators and/or inducers as well as oxidants are then individually fedinto a premix tank. As shown in FIG. 2, from the premix tank, themixture is filtered and passed through a bank of coiled UV transparenttubing wound around a bank of UV light sources bulbs of appropriatewavelength. The coils are inter-linked in series with each other toprovide an efficient rate of conversion to byproducts. The byproductsare gases and water. Returning to FIG. 1, the outlet portion of thephotolysis tubing provides for an outgassing port and a separation valvefor the aqueous solution of byproducts. Appropriate conductance andvolumetric devices may be coupled with the outgassing port andseparation valve to determine the quantity of byproducts beinggenerated. The flow rate of the mixture is adjusted according to therate of byproducts generated. In this fashion, the introduction oforganic and nitrogenous components is balanced to make up for the amountcalculated to be completely converted by the rate of byproductsgenerated.

Alternatively, the mixture from the outlet portion of the coil can berecycled to rephotolyze unreacted organic and nitrogenous components.The gases and aqueous byproducts are drawn off through the out gassingport and separation valve followed by reintroduction of the mixture. Themain tank is monitored as to the concentration of the mixture andsupplemental explosive is added as the concentration decreases.

In an alternative or additional design for the photolytic reactor asshown in FIG. 5, a UV pulsed laser may be used to deliver the UVirradiation through a network of quartz glass fiber optic lines arrangedthroughout an open holding tank or with a cascade apparatus for thesolution and/or suspension of organic and nitrogenous components andorganic solvent. In this manner, slurried amounts of explosivecomponents in addition to those dissolved in the organic solvent can bephotolyzed. Typically, this alternative will utilize a suspension orslurry of small particles of the explosive components in the organicsolvent. The cascade design is shown in FIG. 4. The optical fibers aredesigned to release their energy to the cascading solution orsuspension. The holding or cascade tank can be constructed to handlebatch portions of solutions or suspensions or to carry a continuous flowof solution or suspension slowly past the network of fiber optic coils.With the addition of other lasers with varied wavelengths, the treatmentof the solution or suspension may be tailored to provide a maximizedconversion rate. The use of a pulsed laser and the optic fibers allowsgreater control and minimizes chances for catastrophic failure of thereactor due to any localized exothermic reaction of the solution. Theopen tank design also permits rapid release of large quantities ofgaseous byproducts without gas pressure increases that would interferewith solution or slurry flow or the photolysis process.

The chamber UV reactor can be used in addition to the fiber opticnetwork in the holding tank or cascade to photolyze any remainingquantity of explosive. The solution irradiated by the fiber opticnetwork cascade would subsequently be passed through the UV reactor fora second irradiative treatment. In this fashion, large quantities ofgaseous photolytic products would be removed in the open system usingthe fiber optic network and the more efficient chamber UV reactor wouldcontain the smaller amount of gaseous photolytic product from the secondirradiative treatment until the gases could be evacuated from thechamber outlet.

EXAMPLES

Although the present invention will now be described by reference tocertain preferred embodiments, those with skill in the art willrecognize that many modifications may be made therein without departingfrom the spirit and scope of this invention.

Example 1 Cutting of Munition

This example sets forth a preferred procedure for use of a high pressurejet to remove the explosive from the munition.

The specifications of the munition are determined in order to mark theappropriate positions for cutting of the casing and excavation of theexplosive. For a 30 mm cannon shell of casing thickness 4mm at the baseend, a submerged cutting jet of a mixture of diesel fuel andacetonitrile at a pressure of 150,000 psi is applied to cut a line of adepth of 3.8mm around the base section of the munition. After the firstcut is complete, the pressure of the jet is reduced to 25,000 psi andthe remaining thickness of casing along the cut line is removed.

The severed base section is removed to reveal the RDX, aluminum and waxexplosive packed in the head of the munition. The solvent jet at 15,000psi is trained on the surface of the explosive RDX to slice and excavateit. The pieces of excavated explosive and fluid from the jet arecollected in a depository tank positioned below the munition. Thedepository tank also contained a residual amount of solvent to cover thepieces of explosive that drop into the tank. The excavated explosive inthe tank is slowly stirred to form a suspension the RDX and otherorganic components and a sludge of the aluminum metal. Periodically, thestirring is stopped to allow the sludge to settle to the bottom of thedepository tank. The settled sludge is removed through a bottom drain inthe holding tank. Additional solvent is added to the tank as solvent isremoved through the drain. After the removal of explosive is completeand all explosive has been collected in the depository tank, additionalacetonitrile is added with stirring to dissolve the remaining solidportions of organic components of the explosive. The sludge is againdrained from the bottom of the depository tank and the remainingsolution is pumped through a filter into a photolysis holding tank inpreparation for photolysis.

Example 2 Photolysis of RDX

This example sets forth a preferred procedure for photolysis of theexplosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). The protocolcan be used generally for all secondary explosives.

A solution of RDX in a mixture of 50:50 v/v methylene chloride andacetonitrile may be prepared by dissolving about 1 kg. RDX in 10 L ofthe solvent mixture to yield a 10 percent by weight solution of RDX inthe solvent mixture. The solution may be held in a holding tank fittedwith pressurized inlet and outlet lines to deliver further photolysiscomponents to the tank and the solution to the photolysis reactor.

The continuous cycle photolysis reactor can be constructed of a quartzglass reaction vessel with a central well for a cold cathode mercuryvapor lamp of 20 or more watts per foot output. The vessel is fittedwith an inlet port for connection to the solution delivery line, asystem of internal baffles and fitted partitions for slowing the flow ofthe solution, a fitted outlet for gaseous byproducts and a liquid outletport opposite the inlet port for removal of photolyzed solution.

To study the photolysis, the solution may be pumped from the holdingtank to the photolysis vessel at various rates to determine the rate offlow needed to achieve essentially complete photolysis of the RDX. Themercury lamp is switched on once the solution began to flow in thereaction vessel. The photolyzed solution exiting the outlet port can betransported to a high pressure liquid chromatography (HPLC) apparatus todetermine the amount of RDX remaining. Alternatively, the volume ofexiting byproduct gases and of byproducts contained in the solvent canbe determined by ordinary conductance methods such as those used inconjunction with the output of gas chromatographs.

Example 3 Photolysis with Various Solvents

In this experiment, high and low concentrations of each combination ofsolvent (acetonitrile, methanol and kerosene) and explosive (HMX, RDXand TNT) were UV irradiated and the reactions studied to determine theamount of the unreacted explosive.

Experimental

Explosives were received from Alliant Techsystem Proving Ground (ATPG)and were Military Specification, warhead grade materials. The kerosenewas distilled and blended to ASTM-D3699, K-1 requirements. Reagent gradesolvents were used as received. "Concentrate" solutions were made bysaturating the solvent with the explosive at 22° C. "Diluted" sampleswere prepared by diluting the concentrate by a ratio of 1:2.5 withsolvent. Aliquots of the concentrates and diluted solutions were exposedto ultra violet light (254 um) in a quartz helix (25 mm ID), tubing: 6mm OD wall 1 mm. The solution was not stirred and the exposure time was15 minutes.

Samples of the diluted, exposed diluted and exposed concentrates wereanalyzed for HMX, TNT and RDX where appropriate. The initial concentrateconcentrations were calculated from diluted samples. Standards of HMX,RDX and Octol 70/30 were prepared with concentrations of 107, 113 and167 ppm respectively.

Samples of the starting and photolyzed solutions were analyzed using aWaters HPLC 10 ul, 25 cm Novapak C₁₈, MeOH/H₂ O 70/30(^(v) /v), 1ml/min, 55° C., 240 nm.

Discussion

The data from the experiments are displayed in Table I. The data showthat for HMX the best solvent was acetonitrile (AN) followed by methanol(MeOH) and kerosene (K-1). The same order is true for TNT and RDX. K-1kerosene dissolved only TNT to a significant extent.

Of the explosives used in these experiments, TNT appeared to be the mostsoluble in any of the solvents followed by RDX and then HMX. In AN, thesaturated HMX concentration was about 12450 ppm or 1.6%. The saturatedTNT concentration in AN was about 56221 ppm or 7.2%.

The presence of TNT increases the solubility of HMX in both AN and K-1,MeOH reduced it.

The pure solutions of RDX and HMX in any solvent is very susceptible toalmost complete photolytic destruction based on the concentrations andexposure times given in Table I. The presence of TNT did not inhibit thedestruction of HMX in K-1 and MeOH but appeared to slow HMX destructionin the AN. These data also show the stability of TNT in all solutionsexcept the AN concentrate.

The best solvent for these explosives appears to be acetonitrilefollowed by methanol and kerosene. Destruction of the explosives inthese solvents occurs very readily without additional free radicalagents. The highest concentration measured was 7.2% (w/w) of TNT inacetonitrile.

                                      TABLE I                                     __________________________________________________________________________            Expolsive                                                                     initial                                                                              Final Change                                                                              Initial                                                                              Final Change                                                                             Initial                                                                              Final Change              Sample  PPM HMX                                                                              PPM HMX                                                                             %     PPM TNT                                                                              PPM TNT                                                                             %    PPM RDX                                                                              PPM                                                                                 %DX                 __________________________________________________________________________    SOLVENT: ACETONITRILE                                                         Concentrate 1                                                                         7,858  574   -93                                                      Diluted 1                                                                             3,143  ND    -100                                                     Concentrate 4                                                                         12,450 9,718 -22   56,221 36,126                                                                              -36                                   Diluted 4                                                                             4,980  3,471 -30   22,489 18,919                                                                              -16                                   Concentrate 7                                17,974 2,586  -86                Diluted 7                                    7,190  ND    -100                SOLVENT: KEROSENE                                                             Concentrate 10                                                                        0.85   0.20  -76                                                      Diluted 10                                                                            0.34   0.08  -76                                                      Concentrate 11                                                                        4.90   ND    -100  1,438  971   -32                                   Diluted 11                                                                            1.96   ND    -100    575  112   -81                                   Concentrate 12                               4.45   0.76   -83                Diluted 12                                   1.78   ND    -100                SOLVENT: METHANOL                                                             Concentrate 3                                                                         71     ND    -100                                                     Diluted 3                                                                             28     ND    -100                                                     Concentrate 6                                                                         46     0.48  -99   7,384  4,118 -44                                   Diluted 6                                                                             18     ND    -100  2,953  149   -95                                   Concentrate 9                                1,023  ND    -100                Diluted 9                                    409    ND    -100                __________________________________________________________________________     1 is HMX                                                                      3 is HMX                                                                      4 is HMX/TNT                                                                  6 is HMX/TNT                                                                  7 is RDX                                                                      9 is RDX                                                                      10 is HMX                                                                     11 is HMX/TNT                                                                 12 is RDX                                                                

What is claimed is:
 1. A method for converting an explosive compositioninto non-explosive products comprising:dissolving or dispersing theexplosive composition in an organic solvent to form a mixture; and,irradiating the mixture with ultraviolet light at a wavelength absorbedby the composition to cause conversion of the explosive to thenon-explosive products.
 2. A method according to claim 1 wherein themixture further includes a free radical initiator, a photolytic induceror a combination thereof.
 3. A method according to claim 1 wherein theorganic solvent is an alkyl alcohol, alkyl ketone, alkyl nitrile, nitroalkane, haloalkane or any mixture thereof which is substantiallytransparent to visible light and to ultraviolet light at from about 200to about 400 nanometers.
 4. A method according to claim 1 wherein theconcentration of explosive in the mixture ranges from about 0.5 wt-% tothe lower of the solubility or propagation limit.
 5. A method accordingto claim 2 wherein the free radical initiator is an organic peroxide, apersulfate, hydrogen peroxide or ketones.
 6. A method according to claim5 wherein the mixture further includes an oxidizing agent selected fromthe group consisting of a halogen oxidizing agent, a hydrocarbonoxidizing agent, or mixtures thereof.
 7. A method according to claim 1wherein the ultraviolet light has a wavelength ranging from about 200nanometers to 300 nanometers.
 8. A method according to claim 1 whereinthe ultraviolet light is produced by a mercury lamp having a wavelengthranging from about 245 nanometers to 265 nanometers.
 9. A methodaccording to claim 1 wherein the rate of non-explosive productgeneration is monitored to determine the rate at which additionalnitrogenous and organic explosive components can be added.
 10. A methodaccording to claim 1 wherein the organic solvent is recycled at the endof the process thereby providing a continuous process for the conversionof nitrogenous and organic components of explosives.
 11. A methodaccording to claim 1 wherein said method is performed by a modular,self-contained recycle system.
 12. A method according to claim 1 whereinthe solvent is acetonitrile, methylene chloride or methanol.
 13. Anapparatus for converting an explosive composition into non-explosiveproducts comprising:means for dissolving or dispersing the explosivecomposition in an organic solvent to form a mixture; and, means forirradiating the mixture with ultraviolet light at a wavelength absorbedby the composition to cause conversion of the explosive to thenon-explosive products; the means for irradiating being in fluidconnection with the means for dissolving or dispersing.